Nanoporous metals represent a class of functional materials with applications in catalysis, electrocatalysis, fuel cell technologies, biosensing and material storage, to name a few. Nanoporous palladium, for example, has been shown to have applications in catalysis, electrocatalysis and hydrogen isotope storage and separation. The high surface area to metal volume ratios exhibited by nanoporous palladium, for example, may mitigate the formation of destructive, high-pressure helium bubbles from the decay of tritium stored in palladium lattices.
Common methods for synthesis of porous noble metals include chemical or electrochemical reduction of metal salts in hard or soft polymer templates, dealloying, and aggregation or fusion of precursor nanoparticles. Application of these methods to alloy products can be challenging due to differing nucleation and growth rates of each metal that can result in materials with heterogenous metal distributions that vary widely from the nominal mole fractions of metal precursor used in the methods.
One concern with nanoporous metals is the possibility of pore collapse in applications involving exposing the nanoporous metal to increased temperature. Combining palladium with small amounts of a second, higher melting point metal such as platinum or rhodium to form an alloy has been shown to increase the thermal stability of pores, but pore collapse still occurs in regions of virtually pure palladium.